JPH0552659B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a solid electrolytic capacitor with low loss and good high frequency characteristics. Conventional technology In recent years, with the digitization of electrical equipment,
The capacitors used there also have low impedance in the high frequency range, and there is an increasing demand for smaller size and larger capacity. Conventionally, plastic film capacitors, mica capacitors, multilayer ceramic capacitors, etc. have been used as capacitors for high frequency ranges, but film capacitors and mica capacitors are large in size, making it difficult to increase the capacitance, and multilayer ceramic capacitors Capacitors were created out of a desire for small size and large capacity, but they have drawbacks such as being extremely expensive and having poor temperature characteristics. On the other hand, aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors are used as large capacity capacitors. These capacitors can achieve large capacitance because the oxide film that serves as the dielectric can be made as thin as an elbow, but on the other hand, the oxide film is easily damaged, so an electrolyte is applied between the oxide film and the cathode to prevent damage from time to time. Needs to be repaired. In aluminum dry electrolytic capacitors, etched anode and cathode aluminum foils are wound up with a paper separator in between, and a liquid electrolyte is used. For this reason, it has drawbacks such as a decrease in capacitance and an increase in loss over time due to electrolyte leakage and ionic conductivity, as well as large losses in high frequency characteristics and low temperature regions. . In addition, in aluminum or tantalum solid electrolytic capacitors, the electrolyte is solidified to improve the drawbacks of the aluminum electrolytic capacitors. To form this solid electrolyte, an anode foil is immersed in a manganese nitrate solution and thermally decomposed in a high-temperature furnace at around 350°C to form a manganese dioxide (MnO ₂ ) layer. In the case of this capacitor, since the electrolyte is solid, there are no drawbacks such as electrolyte leakage at high temperatures or functional deterioration caused by solidification at low temperatures, and it shows better frequency and temperature characteristics than liquid electrolytes. The loss in the high frequency range cannot be said to be sufficiently small due to damage to the oxide film due to recurrent decomposition and the high specific resistance of manganese dioxide. Therefore, in order to improve the shortcomings of these capacitors, organic semiconductors with high conductivity and excellent anodic oxidation properties are used as solid electrolytes, such as 7, 7, 8, 8.
It has been proposed to use a -tetracyanoquinodimethane (hereinafter referred to as TCNQ) complex. This organic semiconductor can be applied to the oxide film by dissolving it in an organic solvent or melting it by heating, and can prevent damage to the oxide film due to thermal decomposition that occurs when impregnating MnO ₂ . By using the TCNQ complex, which has high conductivity and good anodic oxidation properties, it is possible to create capacitors with good high-frequency characteristics and large capacity. A technique for using this organic semiconductor as a solid electrolyte is described, for example, in Japanese Patent Application Laid-Open No. 17609/1983 filed by Shinichi Niwa. Problems to be Solved by the Invention According to the invention, the oxide film is impregnated with TCNQ salt by heating and melting the organic semiconductor (TCNQ salt). Immediately after the TCNQ salt melts, the oxide film is immersed, the immersion is completed for a short time until thermal decomposition of the TCNQ salt begins to occur, and then it is rapidly cooled to form microcrystals of the TCNQ salt, It is said that an element with good coverage was obtained. However, TCNQ salt has a high viscosity when melted, and impregnation into the oxide film is insufficient even when immersed for a short time. The present invention solves the above-mentioned problems and provides a method of manufacturing a solid electrolytic capacitor using an organic semiconductor as an electrolyte in a smaller size and larger capacity by improving the impregnating property. Means for Solving the Problems The method for manufacturing a solid electrolytic capacitor according to the present invention comprises a complex salt of 7,7,8,8-tetracyanokydimethane and a neutral 7,
The method includes a step of preparing a mixture of 7,8,8-tetracyanoki dimethane, a step of melting the solid electrolyte, and a step of impregnating the anodic oxide film with the melted solid electrolyte under reduced pressure. Effect The conventional method of melting and impregnating TCNQ salt at normal pressure has a high viscosity when melted and a short time for decomposition, so it can only be immersed for a short time. The etched anodic oxide film could not be sufficiently impregnated and coated. Furthermore, although it is a well-known example that impregnating properties can be improved by performing a reduced pressure impregnation method, it has been impossible to actually carry out this method because the sublimation and decomposition of the TCNQ salt are accelerated. Therefore, we conducted extensive research to find a method to suppress the sublimation and decomposition of TCNQ salt, as well as to reduce its viscosity when melted.We found that adding neutral TCNQ to TCNQ salt can bring about good results. found. Since neutral TCNQ is an insulator, excessive addition increases the resistance value of TCNQ salt, which is a semiconductor.
Although it adversely affects the characteristics of the capacitor, TCNQ
The sublimation that occurs when the salt melts is neutral TCNQ released from the TCNQ salt, so if you add neutral TCNQ in an amount equivalent to the amount released in advance, it will chemically bond during melting and form a salt. So there is no problem. The amount of neutral TCNQ sublimated was less than 5% by weight at atmospheric pressure and about 30% by weight at reduced pressure (10 ^-2 Torr) in the time required for melt impregnation (about 20 seconds). Under these conditions, the optimum amount of neutral TCNQ added is 30% by weight. Organic semiconductor (TCNQ salt) disclosed in the present invention
The manufacturing method for solid electrolytic capacitors using TCNQ as a solid electrolyte involves adding extra neutral TCNQ with high sublimability to TCNQ salt, which suppresses compositional changes in the TCNQ salt and stabilizes it, making it possible to impregnate under reduced pressure. In addition, the addition of neutral TCNQ lowers the viscosity during melting and improves fluidity, which improves the impregnation applicability to the anodized film, which is a fine etching pit, and improves the initial characteristics of the capacitor. It is. Examples Examples of the present invention will be described below. n- synthesized by a method known as an organic semiconductor
Using 100 parts by weight of butylisoquinolinium (TCNQ) ₂ , 2 to 50% by weight of neutral TCNQ was added and mixed well in a mortar. After this, approximately 20 mg was placed in an aluminum can case (diameter 4 mm, height 5 mm).
A rolled-up aluminum electrolytic capacitor unit was placed on top of the capacitor. Heating can be done under reduced pressure, and
An infrared heating device capable of rapid temperature rise was used, and the aluminum can case containing the unit was placed in the heating product holder of this device. First, check the inside of the heating tank for approx.
After reducing the pressure to 10 ^-2 Torr, the temperature was raised to 270°C within 1 second and held at that temperature for 20 seconds to allow the molten TCNQ salt and neutral TCNQ to permeate into the unit. Ta. Thereafter, indoor air was introduced into the heating tank all at once to impregnate the oxide film and simultaneously cool and solidify the organic semiconductor. The initial characteristics of the solid electrolytic capacitor thus obtained are shown in the table in comparison with those obtained without pressure reduction.

【table】

[Table] This shows that as the amount of neutral TCNQ added increases, the capacity increases and the loss decreases.
Addition of 5% by weight without reduced pressure and addition of 30% by weight with reduced pressure showed the best characteristics, respectively. Effects of the Invention In summary, the present invention provides a method for manufacturing a solid electrolytic capacitor characterized by using a reduced pressure impregnation method when impregnating and applying a solid electrolyte to an anodized film. I can do it.

Claims (1)

[Claims] 1 As a solid electrolyte, a complex salt of 7,7,8,8-tetracyanoki dimethane and a neutral 7,
It is characterized by comprising a step of preparing a mixture of 7,8,8-tetracyanoki dimethane, a step of melting the solid electrolyte, and a step of impregnating the anodic oxide film with the melted solid electrolyte under reduced pressure. A method for manufacturing solid electrolytic capacitors.